This command looks wrong. You're mixing chmod and chown syntax here. I suppose what you've meant is
sudo chown 777 -R $USER:$USER $HOME
Still, I advise you against running the second command: although it'll give you full access to all your files, it also will make them all executable and world-writeable in the process. Instead, try this
sudo chown -R $USER: $HOME
chmod -R 777 $HOME
This will give the owner and group members read and write access plus make directories searcheable and retain execute bit on files that already have it set.